ABCC2 regulates vacuolar efflux of phenylalanine and petal development

Plant petals not only possess high ornamental value but also facilitate plant reproduction by attracting insect pollinators. Elucidating the molecular mechanisms of petal development is of vital importance to plant growth and development. Here, we obtained Arabidopsis thaliana mutant atabcc2 and found that atabcc2 displays aberrant petal and floral organ development compared to the wild-type (WT). Compared with WT, auxin levels in seedling leaves, petals and sepals of atabcc2 was significantly reduced, atabcc2 exhibited increased expression of genes involved in phenylalanine (Phe) metabolism (TAT1, TAT2, ADT1, ADT6) and decreased expression of auxin biosynthesis genes (YUC1, YUC7). Phe was found to enhance the expression signal of the pABCC2-GUS construct in Arabidopsis thaliana seedlings and to increase ABCC2 transcript levels in WT. Consistently, Phe treatment restored auxin distribution in atabcc2 floral organs, suggesting that exogenous Phe can increase endogenous auxin levels. Yeast and callus transport assays confirmed that ABCC2 mediates vacuolar efflux of Phe. Additionally, the specific interaction between ABCC2 and TAT1 has been confirmed. GUS signal from YUC1:GUS and TAA1:GUS reporter lines was attenuated in seedlings and petals of atabcc2 compared to WT. Collectively, these findings establish that the interaction between ABCC2 and TAT1 mediates vacuolar efflux of Phe thereby regulating tryptophan-dependent auxin biosynthesis, thus governing petal development in Arabidopsis, which provide new ideas for promoting plant reproduction and boosting crop yield.